Compounds which have retinoid-like activity are well known in the art, and are described in numerous United States and other patents and in scientific publications. It is generally known and accepted in the art that retinoid-like activity is useful for treating mammals, including humans, in order to cure or alleviate the symptoms associated with numerous diseases and conditions.
Retinoids (vitamin A and its derivatives) are known to have broad activities, including effects on cell proliferation and differentiation, in a variety of biological systems. This activity has made retinoids useful in the treatment of a variety of diseases, including dermatological disorders and cancers. The prior art has developed a large number of chemical compounds which have retinoid-like biological activity, and voluminous patent and chemical literature exists describing such compounds. The relevant patent literature includes U.S. Pat. Nos. 4,980,369, 5,006,550, 5,015,658, 5,045,551, 5,089,509, 5,134,159, 5,162,546, 5,234,926, 5,248,777, 5,264,578, 5,272,156, 5,278,318, 5,324,744, 5,346,895, 5,346,915, 5,348,972, 5,348,975, 5,380,877, 5,399,561, 5,407,937, (assigned to the same assignee as the present application) and patents and publications cited therein, which particularly describe or relate to chroman, thiochroman and 1,2,3,4-tetrahydroquinoline derivatives which have retinoid-like biological activity. In addition, several applications are pending which are assigned to the assignee of the present application, and which are directed to further compounds having retinoid-like activity.
U.S. Pat. Nos. 4,740,519 (Shroot et al.), 4,826,969 (Maignan et al.), 4,326,055 (Loeliger et al.), 5,130,335 (Chandraratna et al.), 5,037,825 (Klaus et al.), 5,231,113 (Chandraratna et al.), 5,324,840 (Chandraratna), 5,344,959 (Chandraratna), 5,130,335 (Chandraratna et al.), Published European Patent Application Nos. 0 176 034 A (Wuest et al.), 0 350 846 A (Klaus et al.), 0 176 032 A (Frickel et al.), 0 176 033 A (Frickel et al.), 0 253 302 A (Klaus et al.), 0 303 915 A (Bryce et al.), UK Patent Application GB 2190378 A (Klaus et al.), German Patent Application Nos. DE 3715955 A1 (Klaus et al.), DE 3602473 A1 (Wuest et al., and the articles J. Amer. Acad. Derm. 15: 756-764 (1986) (Sporn et al.), Chem. Pharm. Bull. 33: 404-407 (1985) (Shudo et al.), J. Med Chem. 31: 2182-2192 (1988) (Kagechika et al.), Chemistry and Biology of Synthetic Retinoids CRC Press Inc. 1990 pp. 334-335, 354 (Dawson et al.), describe or relate to compounds which include a tetrahydronaphthyl moiety and have retinoid-like or related biological activity. U.S. Pat. No. 4,391,731 (Boller et al.) describes tetrahydronaphthalene derivatives which are useful in liquid crystal compositions.
An article by Kagechilka et al. in J. Med. Chem 32:834 (1989) describe certain 6-(3-oxo-1-propenyl)-1,2,3,4-tetramethyl-1,2,3,4-tetrahydronaphthalene derivatives and related flavone compounds having retinoid-like activity. The articles by Shudo et al. in Chem. Pharm. Bull. 33:404 (1985) and by Jetten et al. in Cancer Research 47:3523 (1987) describe or relate to further 3-oxo-1-propenyl derivatives (chalcone compounds) and their retinoid-like or related biological activity.
Unfortunately, compounds having retinoid-like activity (retinoids) also cause a number of undesired side effects at therapeutic dose levels, including headache, teratogenesis, mucocutaneous toxicity, musculoskeletal toxicity, dyslipidemias, skin irritation, headache and hepatotoxicity. These side effects limit the acceptability and utility of retinoids for treating disease.
It is now general knowledge in the art that two main types of retinoid receptors exist in mammals (and other organisms). The two main types or families of receptors are respectively designated as the RARs and RXRs. Within each type there are subtypes: in the RAR family the subtypes are designated RAR-.alpha., RAR-.beta. and RAR-.gamma., in RXR the subtypes are: RXR-.alpha., RXB-.beta. and RXR-.gamma.. Both families of receptors are transcription factors that can be distinguished from each other based on their ligand binding specificities. All-trans-RA (ATRA) binds and activates a class of retinoic acid receptors (RARs) that includes RAR-.alpha., RAR-.beta. and RAR-.gamma.. A different ligand, 9-cis-RA (9C-RA), binds and activates both the RARs and members of the retinoid X receptor (RXR) family.
It has also been established in the art that the distribution of the two main retinoid receptor types, and of the several subtypes is not uniform in the various tissues and organs of mammalian organisms. Moreover, it is generally accepted in the art that many unwanted side effects of retinoids are mediated by one or more of the RAR receptor subtypes. Accordingly, among compounds having agonist-like activity at retinoid receptors, specificity or selectivity for one of the main types or families, and even specificity or selectivity for one or more subtypes within a family of receptors, is considered a desirable pharmacological property.
Relatively recently compounds have been developed in the art which bind to RAR receptors without triggering the response or responses that are triggered by agonists of the same receptors. The compounds or agents which bind to RAR receptors without triggering a "retinoid" response are thus capable of blocking (to lesser or greater extent) the activity of RAR agonists in biological assays and systems. More particularly, regarding the scientific and patent literature in this field, published PCT Application WO 94/14777 describes certain heterocyclic carboxylic acid derivatives which bind to RAR retinoid receptors and are said in the application to be useful for treatment of certain diseases or conditions, such as acne, psoriasis, rheumatoid arthritis and viral infections. A similar disclosure is made in the article by Yoshimura et al. J Med. Chem. 38: 3163-3173 (1995). Kaneko et al. Med. Chem Res. 1:220-225 (1991); Apfel et al. Proc. Natl. Acad. Sci. USA 89: 7129-7133 Augusty 1992 Cell Biology; Eckhardt et al. Toxicology Letters 70:299-308 (1994); Keidel et al. Molecular and Cellular Biology 14:287-298 (1994); and Eyrolles et al. J. Med. Chem. 37: 1508-1517 (1994) describe compounds which have antagonist like activity at one or more of the RAR retinoid subtypes.
In addition to undesirable side-effects of therapy with retinoid compounds, there occurs occasionally a serious medical condition caused by vitamin A or vitamin A precursor overdose, resulting either from the excessive intake of vitamin supplements or the ingestion of liver of certain fish and animals that contain high levels of the vitamin. The chronic or acute toxicities observed with hypervitaminosis A syndrome include headache, skin peeling, bone toxicity, dyslipidemias, etc. In recent years, it has become apparent that the toxicities observed with vitamin A analogs, i.e., retinoids, essentially recapitulate those of hypervitaminosis A syndrome, suggesting a common biological cause, i.e., RAR activation. These toxicities are presently treated mainly by supportive measures and by abstaining from further exposure to the causative agent, whether it be liver, vitamin supplements, or retinoids. While some of the toxicities resolve with time, others (e.g., premature epiphyseal plate closure) are permanent.
Generally speaking, specific antidotes are the best treatment for poisoning by pharmacological agents, but only about two dozen chemicals or classes of chemicals out of thousands in existence have specific known antidotes. A specific antidote would clearly be of value in the treatment of hypervitaminosis A and retinoid toxicity. Indeed, as increasingly potent retinoids are used clinically, a specific antidote for retinoid poisoning could be life saving.